One known projectile 1 of this type is shown in FIGS. 1a to 1c. It includes a cup 5 that is intended to contain and protect a tail fin assembly of the projectile 1 during the storage and transport operations, and above all during the gun firing phase of the projectile.
A rotating band 3 of the projectile is there to provide sealing against gases between the projectile and the gun during firing of the projectile.
In order to protect the contents of the cup 5 from the corrosive effects of the firing gases, it is known to use a collar 4 that is centered by an annular part 4a on the projectile. The cup 5 comprises a wall 5b that extends from the bottom of the cup to below the collar 4.
An O-ring 8 is centered on the body 2 of the projectile 1 and pinches the edge of the wall 5b against the inside of the collar 4.
In this way, the firing gases cannot penetrate the cup 5 at the edge 5c of the wall 5b. 
Upon leaving the gun, the shell 5 is separated from the rest of the projectile by means known by the person skilled in the art and as disclosed in patent EP 1,297,292, for example.
The rotating band 3 is in turn dislocated due to the rotation of the projectile, which improves the overall aerodynamics of the projectile by reducing the surface opposing the forward motion.
However, it remains an aerodynamic brake formed by a bulge of the projectile 1 body 2. This bulge forms a shoulder oriented toward the front of the projectile to serve as support for the annular part 4a of the collar 4.
It forms a first obstacle to the flow of air. The bulge includes a groove 7 that receives the O-ring 8, this groove causes a discontinuity in the flow of air (FIG. 1c), which forms a second aerodynamic brake and thus limits the range of the projectile.
Patent EP 1,297,292 describes one such type of known projectile.